Multi-function communication devices such as smart phones allow their users to perform several other electronic tasks while simultaneously participating in a call. For instance, the user of the device an surf the Web, check her calendar, navigate a map, or find an address in a contacts list while simultaneously on a call with a far-end user.
Many users also like to enable sound feedback on their device, so that they can hear their own mouse clicks and message alerts clearly and easily. For example, when a message is received in the user's inbox, whether it be an email, voicemail, or an SMS text message, a prerecorded or synthesized audible tone is played through a speaker of the device to alert the user of the new message or update. Such clicks and alerts are referred to here generally as user interface (“UI”) audible tones, referring generally to sound in the audible frequency range that is produced as a result of an event occurring in an application to which the user should be alerted (hence the reference to “user interface”). The user can typically set the loudness of such UI tones through, for instance, the volume setting switch typically found in such devices. More generally, UI tones can be any sound generated intentionally through a speaker of the device or an external speaker that is connected to the device, such as the built-in ear speaker, loudspeaker, headphones, or an externally connected speaker. UI tones can be clicks and alerts as noted previously, or they can be music or gaming audio, or audio mixes of these. Typically, the UI tones are of interest only to the near-end user of the device and are distracting or annoying to the far-end user on the other end of a voice call, and thus it is desirable to prevent the unintentional transmission of these UI tones to the far-end user.